1 Reactions in Aqueous Solutions I

2 Properties of Aqueous Solutions of Acids & Bases Acidic properties taste sour change the colors of indicators turn litmus red react with metals to generate H 2(g) react with carbonates and bicarbonates to form salts, carbon dioxide and water aqueous solutions conduct electricity react with bases to produce salt and water

3 Properties of Aqueous Solutions of Acids & Bases Basic properties taste bitter feel slippery change colors of indicators turn litmus blue react with acids to form salts and water aqueous solutions conduct electricity SOAP

4 Arrhenius Acid Acid - A substance that produces hydrogen ions, H +, in aqueous solutions. HCl  H + + Cl - HCN  H + + CN -

5 Arrhenius Base Base - A substance that produces hydroxide, OH -, in aqueous solutions. KOH  K + + OH - NH 3 + H 2 O  NH OH -

6 Arrhenius Theory neutralization - combination of H + (or H 3 O + ) with OH - strong acids - ionize 100% in water HCl, HBr, HI, H 2 SO 4, HNO 3, HClO 4 strong bases - ionize 100% in water LiOH, NaOH, KOH, RbOH, CsOH, Ca(OH) 2, Sr(OH) 2, Ba(OH) 2

7 Arrhenius Theory total ionic equation for strong acid with strong base

8 Arrhenius Theory net ionic equation for strong acid with strong base

9 Acid-Base Theories The most general theory for common aqueous acids and bases is the BRØNSTED - LOWRY theory ACIDS DONATE H + IONS BASES ACCEPT H + IONS

10 Acid-Base Theories ACIDS DONATE H + IONS BASES ACCEPT H + IONS

11 Brønsted-Lowry Acid-Base Theory differences between Arrhenius & Brønsted-Lowry theories reaction does not have to occur in an aqueous solution bases do not have to be hydroxides for example- ammonia is not a hydroxide NH 3 + H 2 O  NH OH -

12 Hydronium Ion The hydrated hydrogen ion or hydronium ion gives aqueous solutions of acids their characteristic acidic properties. H 2 O + H +  H 3 O + hydronium ion

13 Hydrated Hydrogen Ion H + (aq) is really H(H 2 O) n + n is a small integer = 7? H 3 O + is usually used where n = 1 H 3 O +  H +

14 Acid-Base Characteristics Solution TypeRelationship Acid[H + ] > [OH - ] Neutral[H + ] = [OH - ] Base[H + ] < [OH - ]

15 Brønsted–Lowry Acids An acid is a proton donor. HNO 3 + H 2 O  H 3 O + + NO 3 -

16 Brønsted–Lowry Bases A base is a proton acceptor. NH 3 + H 2 O  NH OH -

17 Brønsted–Lowry Acids and Bases The Brønsted definition means NH 3 is a BASE in water — and water is itself an ACID.

18 Brønsted–Lowry Acids and Bases An acid–base reaction is the transfer of a proton from an acid to a base. HCl + H 2 O  H 3 O + + Cl - acid 1 base 2

19 Brønsted–Lowry Acids and Bases When an acid gives up a proton, a conjugate base is formed that is capable of accepting a proton.

20 Brønsted–Lowry Acids and Bases HF + H 2 O  H 3 O + + F - acid 1 base 2 base 1 acid 2

21 Conjugate Acid-Bases Conjugate acid- base pairs are a reactant and a product that differ by a proton, H +.

22 Conjugate Acid-Bases Conjugate acid-base pairs are a reactant and a product that differ by a proton, H +.

23 Conjugate Acid-Bases Every acid has a conjugate base, formed by the removal of a proton from the acid. Every base has a conjugate acid associated with it, formed by the addition of a proton to the base. Thus H 3 O + is the conjugate acid of H 2 O.

24 Conjugate Acid-Bases HNO 2 + H 2 O  H 3 O + + NO 2 - Conjugate base Acid Base Conjugate acid

25 Conjugate Acid-Bases NH 3 + H 2 O  NH OH - Conjugate acid Base Conjugate base Acid

26 Conjugate Acid–Base Strengths The more readily a substance gives up a proton, the less readily its conjugate base accepts a proton. The more readily a base accepts a proton, the less readily its conjugate acid gives up a proton.

27 Conjugate Acid–Base Strengths The stronger an acid, the weaker its conjugate base. The weaker an acid, the stronger its conjugate base.

28 Conjugate Acid–Base Strengths

29 Ampholytes A substance capable of being an acid or a base is amphoteric. H 2 O + H 2 O  H 3 O + + OH - acid 1 base 1 acid 2 base 2

30 Bronsted-Lowry Acid-Base Theory water can be either an acid or base in Bronsted-Lowry theory amphoteric - species that can be either an acid or base amphiprotic - proton transfer reactions that species behave as either an acid or base